Ruairí Ó Brádaigh, whose life- long commitment to an interpretation of Irish republicanism was matched only by the fervour with which he opposed any compromise of its principles, has died aged 80.

Des Dalton, his successor as president of Republican Sinn Féin, the party he founded in 1986, eulogised him last night as “a towering figure of Irish republicanism in the latter half of the 20th century”.

“He came to embody the very essence of the Republican tradition, setting the very highest standards of commitment, duty, honour and loyalty to the cause of Irish freedom,” Mr Dalton said.

Gerry Adams, the president of Sinn Féin who was loathed by Ó Brádaigh, spoke of his “sadness” at his death.

“On behalf of Sinn Féin, I want to extend my sincere condolences to his family and friends,” he said. “Whatever differences we may have shared on political matters, Ruairí was a life-long activist who was committed to his principles.”

Longford backgroundBorn Peter Roger Casement Brady, he grew up in a middle-class family in Longford. His mother, Mary Caffrey, had been in Cumann na mBan, the female wing of the Irish Volunteers, the forerunner organisation of the Irish Republican Army.

His father, Matt Brady, was a member of the Volunteers and died when Brady was just 10 years old.

At the age of 18, Brady joined Sinn Féin and, the following year while studying commerce at University College Dublin, he also joined the IRA, the party’s illegal military wing.

At college, he obtained a certificate in teaching Irish and a teaching position with Roscommon Vocational Education Committee followed, by which time Brady had changed his name to the Irish version, Ó Brádaigh. One of his earliest actions as an IRA man was to participate in the unveiling of a statue in Dublin’s Fairview Park to Seán Russell, a former “chief of staff” of the IRA whose Berlin dalliance with German intelligence led to accusations of collaboration with the Nazis.

In the mid-1950s, Ó Brádaigh was running IRA training and was instructed by the organisation’s ruling army council to lead a raid on a barracks in Berkshire, England.

The raid netted 55 Sten sub- machine guns and almost 90,000 bullets, but they all were soon recovered by police.

In 1956, Ó Brádaigh was responsible for training IRA men for the organisation’s so-called Border campaign.

He participated personally in an armed assault on a police station in Derrylin in Co Fermanagh, during which an RUC constable, John Scally, was murdered.

Ó Brádaigh was one of several people arrested in the Republic after the raid and was jailed for six months for failing to explain to the Garda what they had been doing.

Elected to DáilIn 1957, he was elected to the Dáil for Longford-Westmeath, but, because of Sinn Féin’s then policy of not recognising the State and abstaining from full participation in politics, he did not take his seat. He lost it in the 1961 general election.

In October 1958, he was appointed chief of staff of the IRA, a position he held until the following year when Seán Cronin, subsequently this newspaper’s Washington correspondent, took over, Ó Brádaigh assuming the post of adjutant general to Cronin.

Throughout much of the 1960s, Sinn Féin and the IRA were largely inactive but the advent of the modern-day Troubles in Northern Ireland in 1969 boosted the organisation.

Under Ó Brádaigh’s leadership of what was then known as Provisional Sinn Féin, successive leaders of the (Provisional) IRA, notably Seán Mac Stiofáin and Dáithí Ó Conaill, orchestrated a sustained campaign of bombing and shooting in Northern Ireland, the Republic, Britain and, occasionally, continental Europe.

Ó Brádaigh remained implacably opposed to the compromises of the peace process as it developed throughout the late 1980s and 1990s. He founded Republican Sinn Féin in opposition to the peace process, earning the sobriquet “dissident” from the Adams-McGuinness leadership. In 2005, the party offices on Dublin’s Parnell Street sported a façade banner proclaiming “100 years unbroken continuity”.

Continuity was an important concept and word for Ó Brádaigh and the so-called Continuity IRA, of which Ó Conaill was first chief of staff, is linked to Republican Sinn Féin by police and military in both the Republic and Northern Ireland.

It has been involved in several shooting incidents, including the 2009 murder of Constable Stephen Carroll, the first member of the PSNI member to be killed.

Those responsible were described at the time by Sinn Féin’s Deputy First Minister Martin McGuinness as “traitors to the island of Ireland”.

Ruairí Ó Brádaigh is survived by his widow, Patsy, their six children, grandchildren and a great-grandchild.